The error states that Alfresco is looking for a web script called /slingshot/zipContents and is not finding it. Assuming your JAR contains that web script, did you restart Alfresco after you placed the JAR in the lib directories?
Also, what version are you using? The Download as Zip action became part of the core product a couple of releases ago.
Alfresco version is Alfresco Community v4.0.0. When I place jar and start the tomcat. The UI appeared in the Repository in selected Item box. Only process is not OK. Is there any additional code after put the two jar?